1. Field of the Invention
This invention relates to cylinder units, particularly to a double acting cylinder unit having inner and outer double-wall cylinder tubes, which form a fluidal path therebetween, and capable of desirably performing piping at the front or rear side of a cylinder, differing in direction from each other.
2. Related Art Statement
The following can be listed as a double acting cylinder unit.
More specifically, it is a double acting cylinder unit including: two spaces in a cylinder bore, partitioned by a piston; a pair of feed-exhaust ports for feeding pressurized fluid into these two spaces so as to drive the piston; and a pair of communication passages for communicating the pair of feed exhaust ports with the two spaces in the cylinder bore. The pair of feed-exhaust ports of this double acting cylinder unit are separately provided on the front and rear sides of the cylinder, or provided on either the front or rear side. For example, as an example of the former, one feed-exhaust port is provided in a rod cover and the other feed-exhaust port is provided in a head cover. In contrast thereto, as an example of the latter, the pair of the feed-exhaust ports are provided in either the rod cover or the head cover.
However, in the former double acting cylinder unit, i.e. the one wherein the pair of the feed-exhaust ports are separately provided on the front and rear sides of the cylinder out of the above-described constructions, the pair of feed-exhaust ports are located at positions separate of each other, whereby routes of pipings connected thereto become so complicated as to require a large piping space, and moreover, the mounting work and maintenance become disadvantageously troublesome.
In this respect, the latter double acting cylinder unit, having the pair of feed-exhaust ports being provided at either the front or rear side, has not the problem as the former double acting cylinder unit has.
However, the latter double acting cylinder unit, having the pair of feed-exhaust ports being provided only at one side of the cylinder, such a disadvantage is presented that piping can be performed only from the feed-exhaust ports positioned at one side, whereby piping from the other side cannot be carried out. For example, should some covering article be present in front of the feed-exhaust ports, piping cannot be carried out.
In this case, it is conceivable that component parts of the double acting cylinder unit are disassembled and suitably reassembled such that the feed-exhaust ports are positioned in the opposite direction. However, in general, in the double acting cylinder unit of the type described, only one pair of communication passages for communicating the pair of feed-exhaust ports with the first and second spaces in the cylinder bore are presupposed, so that it is difficult to easily and quickly change the positions of the feed-exhaust ports by the above-described disassembling and reassembling works.